<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var a = 5;
        b = 9;
        function fun() {
            var a = 13;
            b = 3;
        }
        console.log("a = " + a  + " b = " + b); // a = 5 b = 9
        fun();
        console.log("a = " + a  + " b = " + b); // a = 5 b = 3
    </script>
</body>
</html>